The use of aluminum for automotive engine blocks offers the potential for considerable weight savings in vehicles and for improvements in fuel economy. However, after several decades of attempts no aluminum alloy has been developed or identified that provides the required combination of casting, machining and wear resistance properties for cylinder block manufacture and service. Aluminum alloys that have provided resistance to piston wear have been difficult to cast into the intricate shapes of the cylinder blocks and have been difficult to machine to the finish dimensions required. Aluminum alloys that can be suitably cast and machined to make cylinder blocks have lacked cylinder wall wear resistance in service. Engine manufacturers have tended to select castable and machinable alloys and modify the surfaces of the cylinder walls to obtain the necessary wear resistance.
Thus, when current cylinder blocks are cast of alloys such as Aluminum Alloy 319 or AA 356 they require cylinder liners (cast iron, metal matrix composite, AA390) or surface treatment (plating, coating) to provide wear resistance during operation. Cast iron liners have been placed like cores in the casting mold for inclusion in the blocks or inserted in the machined cylinder bores. Other wear resistant liner compositions have also been used. As an alternative to cylinder liners, wear resistant coatings have been applied to the cylinder walls of the cast and machined block. Each of these modifications to the block increases the cost of the product.
There remains a need for an aluminum alloy that provides all of the above properties for cylinder block manufacture and wear properties. It is an object of this invention to provide such material.